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What is a Fault in Tennis? Definition, Rules, Tips, and Stats

What is a Fault in Tennis?

Definition, Rules, Tips & Stats

By Jon Crim

Faults, including service and foot faults, are an integral part of the game that can directly influence the outcome of a match.

Whether you’re new to tennis or watching a tournament and looking for a refresh on the topic, it’s not uncommon to need clarification on what constitutes a fault and the subject’s nuances.

This guide fully explores faults in tennis, providing a concrete definition, explaining the rules, reviewing the different types, and sharing the top causes and tips for reducing them.

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What is a Fault?

For every point in a tennis match, players have two opportunities to serve a ball into the correct service box to initiate play.

When a player loses their first serve, it’s called a fault. A subsequent loss of their second serve is a double fault, which results in the serve losing the point. There are various reasons an umpire or linesperson might call a fault on a player’s first or second serve, so let’s dig into those next.

Types of Faults & Rules

In tennis, there are two types of faults. Although the consequence of each is the same, the causes are distinct.

Service Fault

A service fault is the most common, regularly occurring throughout a match. According to the International Tennis Federation’s (ITF) Rules of Tennis, the umpire can call a service fault for any of the following reasons.

  • Breaking Rule 16, 17, or 18; or
  • The server misses the ball when trying to it; or
  • The ball served touches a permanent fixture, singles stick, or net post before it hits the ground; or
  • The ball served touches the server or server’s partner or anything the server or server’s partner is wearing or carrying.

Additional examples of permanent fixtures include back or sidestops, spectators, seats, stands, umpires, and ball persons.

Rule 16: The Service

Before a player starts into their service motion, they must stand still with both feet behind the baseline on the correct half of the court, i.e., to the left or the right of the service mark.

Next, the server releases the ball by hand with their racquet before the ball drops to the ground, and they complete their service motion after hitting or missing the ball. It’s worth noting that players with only one arm can use the racquet to release and hit the ball.

If a player does not adhere to the above requirements, the umpire will call a fault. For example, it’s a fault if the server walks to the baseline and moves directly into their service motion without standing at rest.

As another example, if a server bounced the ball and served it off the bounce in the air, it’s a fault.

Rule 17: Serving

In a standard game, the server starts by standing behind the baseline on the right half of the court and attempts to serve diagonally into the opposite service box on their opponent’s end.

The server has two attempts to make their serve. If they miss their first attempt to hit their serve into the correct service box, it’s a fault. The second miss of their serve results in a double fault causing the server to lose the point.

Foot Fault

An umpire or line judge can also call a foot fault, which has the same implications as a service fault. The causes of a foot fault include any of the following reasons according to Rule 18 of the ITF:

  • Change position by walking or running, although slight movements of the feet are permitted; or
  • Touch the baseline or the court with either foot; or
  • Touch the area outside the imaginary extension of the sideline with either foot; or
  • Touch the imaginary extension of the center mark with either foot.

Foot faults are rare compared to service faults, especially on the ATP and WTA professional tours.

Helpful Tip

It’s worth noting that players can leap over the baseline and into the court as part of their motion as long as they don’t touch it. Pushing off the ground and over the baseline is normal and happens on most serves.

However, leaping into the air while serving wasn’t always allowed. Before 1958, the rules dictated that players needed to keep one foot in contact with the ground before hitting the ball.

Serve and volleyers are often foot fault culprits as their style of play requires them to quickly move to the net after serving.

Service ‘Let’ as a Fault

A service let does not constitute a fault. You’ll most commonly hear an umpire call a let when the ball touches the net, strap, or band and subsequently lands in the correct service box.

If a let happens on a first serve, the point restarts and the server is allowed two additional serves. On a second serve, the server is only allowed an extra serve. There is no limit to the number of service lets that can occur during a single point.

In rarer cases, a let will result if the ball touches the net, strap, or band and hits the receiver, their partner, or anything they wear or carry before hitting the ground.

For example, if the serve hits the net, then bounces off their opponent’s racquet before hitting the ground, regardless of whether it was going to land in the service box, it’s a let. This scenario would be more likely to occur in doubles, but it’s not impossible in singles.

Top Causes of Faults

As we’ve covered, various scenarios can result in a fault, but the most common is under the server’s control. Here are some of the most common reasons resulting in a tennis fault.

Poor positioning

When you step to the baseline, if you’re not paying close attention to the positioning of your feet, you’re setting yourself up for a foot fault. It tends to happen more often when players are flustered or in a rush.

Inaccurate toss

A poorly executed serve toss can wreak havoc on the accuracy of a player’s serve, resulting in unnecessary faults that can cost players a match. Although it’s common for players to practice their serve heavily, the toss is often underemphasized and not given enough attention.

Lack of Spin

Players can increase their margin for error by hitting higher above the net with spin, which brings the ball back down into the service box. If enough spin isn’t applied, the ball often sails long, resulting in a fault.


Wind can make it more difficult to toss the ball accurately and successfully hit a serve into the service box. To combat wind and reduce service faults, players will lower their toss, hit with less power, and apply more spin for added control.


Serving into the sun can make it challenging to see, causing a player’s form to suffer, which leads to unnecessary faults. To manage the sun while serving, players can change their position along the baseline, modify their toss location, or wear a hat.

Tips for Reducing Faults

Faults are inevitable, but there are steps you can take to decrease the likelihood that they occur. Here are some tips for reducing them.

Give Yourself Space

The easiest way to prevent foot faults when hitting a serve is to avoid standing too close to the baseline. By giving yourself space, you help ensure any forward movement of your front foot during your service motion doesn’t contact the baseline.

If you still find yourself committing foot faults, try placing an item such as a cone or an empty ball to provide a physical boundary between you and the baseline, which will help you identify when you’re crossing it.

I’d also encourage you to try recording yourself serving to better understand the part of your motion resulting in the foot fault. Players usually become more aware of their movement after a video.

Work on Your Toss

A well-tossed ball is essential for an effective serve and avoiding faults, but most players rarely work on their toss independent of their serve. If you suspect your toss is causing you problems, find a few drills for improving it and make time to practice it repeatedly.

It takes time and patience to develop a toss you can rely on, but it’s well worth the effort if it’s costing you in your matches.

Set Your Feet

Establishing and maintaining balance while serving is essential to avoid a poor serve that results in a fault. Before serving, take a brief moment to set your feet and pause before starting into your service motion to improve your balance. Doing so will help prevent you from rushing, making it difficult to balance and successfully execute your serve.

Establish a Routine

Another way to help prevent foot faults is establishing a pre-serve routine, providing a rhythm or flow that improves consistency.

Here’s an example:

  1. Always collect two balls
  2. Step up to the baseline
  3. Set your feet behind the baseline
  4. Bounce the ball a specific number of times
  5. Touch the ball to the throat of your racquet
  6. Start into your service motion

The specifics of your routine are less important than consistently executing it, which helps build muscle memory for better consistency while reducing the likelihood of a fault.

Go For Less

Overhitting is one of the top causes of service faults, which happens when players attempt to hit their serve too hard. Although a fast serve can be a powerful weapon, so can an accurate serve with less pace. Go for less on your serve to improve your serving percentage and reduce the likelihood of a fault.

Famous Faults & Statistics

Although rare, a handful of foot faults stand out in history. I’ve pulled together those and a selection of unique stats about faults.

Famous Faults

On the pro tour, you won’t see foot faults called too often as players have finely tuned service routines and motions from thousands of hours of practice. As a result, when umpires call foot faults, it’s usually a surprise that can result in players getting frustrated and losing focus.

Serena Williams 2009 US Open

In the semi-final of the 2009 US Open, Serena Willaims was down a set and serving at 5-6 with a score of 15-30 when a lineswoman called her for a footfault on her second serve. In response, Serena told the lineswoman:

“I swear to God I’m [expletive] going to take this [expletive] ball and shove it down your [expletive] throat.”

As a result of the foot fault, the score moved to 15-40. However, what Serena said to the lineswoman constituted a second warning resulting in a point penalty which handed the match to her opponent Kim Clijsters.

Andy Roddick 2010 US Open

During the 2010 US Open, Andy Roddick played Janko Tipsarevic in the second round when a line judged called a foot fault. After the call, Roddick asked whether it was his right or left foot, and the lineswoman told him it was his right foot when asked.

Convinced he never would foot fault with his right foot, he went on a short tirade complaining to the umpire. However, a replay showed that he did foot fault, but it was his left foot, which he learned after the match.

Lleyton Hewitt US Open 2001

Playing James Blake in the 2001 US Open, a linesperson called Lleyton Hewitt for his second foot fault of the match.

Hewitt commented to the umpire, “Look at him. Look at him. You tell me what the similarity is.”

Lleyton was, of course, referring to the fact that both the linesperson and James Blake are black, insinuating preferential treatment in an ugly example of what can unfold when players lose their temper.

Fault Statistics

The following are a handful of noteworthy double faults facts and statistics from the ATP and WTA during the open era.

Most Double Faults in a Match – ATP

Swiss tennis player Marc Rosset racked up 31 double faults during his loss to French tennis player Arnaud Clement in the quarter-finals of the 2001 Davis Cup, the most of any male.

Most Double Faults in a Match – WTA

Anna Kournikova served more double faults than any other woman during her second-round win at the 1999 Australian Open.

ATP Double Fault Leaders

In 2021, here are the ATP players with the highest average double faults per match.

Player Avg. Double Faults/Match
Benoit Paire 7.9
TBAlexander BublikD 6.7
Denis Shapovalov 5.9
Gael Monfils 5.0
Botic van de Zandschulp 4.4
Dominik Koepfer 4.3
Felix Auger-Aliassime 42
Egor Gerasimov 4.2
Fabio Fognini 4.2
Jeremy Chardy 4.1

WTA Double Fault Leaders

In 2021, here are the WTA players with the most double faults.

Player 2021 Double Faults
Aryna Sabalenka 338
Paula Badosa 305
Karolina Pliskova 295
Elise Mertens 294
Coco Gauff 256
Camila Giorgi 247
Kristina Mladenovic 246
Jelena Ostapenko 237
Ekaterina Alexandrova 230
Ana Konjuh 228

Is there a specific data point about faults that you’d like to know? Let me know in the comments below, and I’ll do my best to add it.

Wrapping Up

It’s easy to understand why a fault in tennis might need clarification, as even the most experienced players periodically require a refresher on the nuances of the rules, so I hope you found this review helpful.

If you have any follow-up questions about the material I covered or anything you’d like to share on the topic, I’d love to hear from you in the comments below.

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